Method for build separation from a curing interface in an additive manufacturing process

ABSTRACT

A layer-by layer method for additive manufacturing that includes: photocuring a first volume of resin to form a layer of a build at an upper surface of a separation membrane laminated over a build window; injecting a fluid into an interstitial region between the separation membrane and the build window; retracting the build from the build window; evacuating the fluid from the interstitial region; and photocuring a second volume of liquid resin to form a subsequent layer of the build between an upper surface of a separation membrane and the previous layer of the build.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of U.S. patent application Ser. No.16/900,560, filed on 12 Jun. 2020, which is a continuation of U.S.patent application Ser. No. 16/672,410, filed on 1 Nov. 2019, whichclaims the benefit of U.S. Provisional Application No. 62/754,411, filedon 1 Nov. 2018, each of which is incorporated in its entirety by thisreference.

U.S. patent application Ser. No. 16/900,560, filed on 12 Jun. 2020, isalso a continuation of U.S. patent application Ser. No. 16/672,415,filed on 1 Nov. 2019, which claims the benefit of U.S. ProvisionalApplication No. 62/754,430, filed on 1 Nov. 2018, each of which isincorporated in its entirety by this reference.

TECHNICAL FIELD

This invention relates generally to the field of additive manufacturingand more specifically to a new and useful method for build separation ina digital light process in the field of additive manufacturing.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flowchart representation of a method.

FIGS. 2A and 2B are schematic representations of a system;

FIGS. 3A and 3B are schematic representations of the system;

FIGS. 4A and 4B are schematic representations of the system;

FIGS. 5A and 5B are schematic representations of the system;

FIG. 6 is a schematic representation of the system;

FIG. 7 is a schematic representation of the system;

FIG. 8 is a flowchart representation of the method;

FIG. 9 is a flowchart representation of the method;

FIG. 10 is a flowchart representation of the method;

FIG. 11 is a flowchart representation of the method; and

FIGS. 12A, 12B, and 12C are flowchart representations of the method.

DESCRIPTION OF THE EMBODIMENTS

The following description of embodiments of the invention is notintended to limit the invention to these embodiments but rather toenable a person skilled in the art to make and use this invention.Variations, configurations, implementations, example implementations,and examples described herein are optional and are not exclusive to thevariations, configurations, implementations, example implementations,and examples they describe. The invention described herein can includeany and all permutations of these variations, configurations,implementations, example implementations, and examples.

1. Method

As shown in FIG. 1, a method for additive manufacturing includes:photocuring a first volume of resin to form a first layer of a build atan upper surface of a separation membrane laminated over a build window,the first layer of the build adhering to a build platform in Block S110;injecting a fluid into an interstitial region between the separationmembrane and the build window in Block S120; retracting the buildplatform from the separation membrane in Block S130; evacuating thefluid from the interstitial region to peel the separation membrane fromthe first layer of the build in Block S140; and photocuring a secondvolume of liquid resin to form a second layer of the build between theupper surface of the separation membrane and the first layer of thebuild in Block S150.

Also shown in FIG. 1, one variation of the method S100 includes:photocuring a first volume of resin to form a first layer of a build atan upper surface of a separation membrane laminated over a build windowin Block S110; injecting a fluid into an interstitial region between theseparation membrane and the build window in Block S120; retracting thefirst layer of the build from the build window in Block S130o;evacuating the fluid from the interstitial region in Block S140; andphotocuring a second volume of liquid resin to form a second layer ofthe build between an upper surface of a separation membrane and thefirst layer of the build in Block S150.

As shown in FIG. 11, one variation of the method S100 includes:photocuring a first volume of resin to form a first layer of a build atan upper surface of a separation membrane laminated over a build window,the first layer of the build adhering to a build platform in Block S110;injecting a fluid into an interstitial region between the separationmembrane and the build window in Block S120; retracting the buildplatform from the separation membrane in Block S130; evacuating thefluid from the interstitial region to peel the separation membrane fromthe first layer of the build in Block S140; advancing the build platformtoward the build window to a target position above the separationmembrane laminated to the build window, the target position based on alayer thickness parameter of the build in Block S142; and photocuring asecond volume of liquid resin to form a second layer of the buildbetween the upper surface of the separation membrane and the first layerof the build in Block S150.

As shown in FIGS. 12A, 12B, and 12C, another variation of the methodS100 includes: during a first photocuring phase, photocuring a firstvolume of liquid resin to form a first layer of a build between an uppersurface of a separation membrane laminated to a build window and a buildplatform in Block S110; during a pressurization phase subsequent to thefirst photocuring phase, injecting a fluid into an interstitial regionbetween the separation membrane and the build window in Block S120;during a retraction phase, retracting the build platform from the buildwindow in Block S130; during a relamination phase subsequent to thepressurization phase, evacuating the fluid from the interstitial regionto peel the separation membrane from the first layer of the build andlaminate the separation membrane to the build window in Block S140; and,during a second photocuring phase subsequent to the relamination phase,photocuring a second volume of liquid resin to form a second layer ofthe build between an upper surface of a separation membrane and thefirst layer of the build in Block S150.

2. Applications

Generally, an additive manufacturing system 100 (hereinafter “the system100”) executes the method S100 to selectively irradiate resin, via astereolithographic process—such as a digital light process (hereinafter“DLP”) or a continuous digital light process (hereinafter “CDLP”)—tocure successive layers of a solid, physical object or set of objects(hereinafter “a build”). In a standard bottom-up stereolithographicadditive manufacturing system, a layer of resin may tend to adhere (or“stick”) to the surface of a build window within this additivemanufacturing system when photocured (e.g., via exposure to specificwavelength(s) of electromagnetic radiation); this layer of cured resinis then separated from this build window prior to advancement of a buildplatform (to which the build is adhered) and prior to introducing andphotocuring a subsequent layer of resin. The resulting force from thisseparation can: deform the intermediate state of the ongoing build (inits “green” state) resulting in poor dimensional accuracy; increase theprobability of build failure; and reduce print speeds, amongst otherissues. The system 100 reduces these separation forces via inclusion ofa replaceable separation membrane 160 (laminated over the upper surfaceof a build window 110 during a photocuring phase of a build process),which functions to limit adhesion forces (e.g., Stefan adhesion, suctionforces) between newly cured layers of the build and the build window110. Additionally, the system 100 includes a pressure regulation system190 (e.g., a compressor/pump, and/or valve system) to selectively injectfluid (i.e. gases or liquids transmissive to electromagnetic radiationprojected by a projection system 120) into an interstitial regionbetween the build window 110 and the separation membrane 160 to obviateany need to directly separate a newly cured layer of the build from aninflexible build window during advancement of a build platform (as wouldbe executed in a standard bottom-up stereolithographic processo.

In particular, the system 100 executes a build cycle to cure a new layerof a build; to separate the separation membrane 160 from the buildwindow 110, and the newly cured layer of a build from the separationmembrane 160; and to advance in preparation for curing a subsequentlayer of the build. The build cycle includes: a photocuring phase (BlockS110) to selectively photocure a layer of resin according to thecross-sectional geometry of the build; a pressurization phase (BlockS110) to inject fluid into the interstitial region between theseparation membrane 160 and the build window 110 thereby facilitatingseparation of the separation membrane 160 from the build window 110; aretraction phase (Block S130) to fully separate the separation membrane160 from the build window 110 and to begin separating or fully separatethe build (in its “green state”) from the separation membrane 160 bypeeling (e.g., via a vector separation process) the separation membrane160 away from the newly cured layer; and a relamination phase (BlockS140) to evacuate fluid from the interstitial region therebyrelaminating the separation membrane 160 against the build window 110 inpreparation for photocuring a subsequent layer. Once the system 100 hasexecuted a build cycle, the system 100 can execute a second photocuringphase (Block S150) to form the subsequent layer of the build. In oneimplementation, the method S100 can also include an advancement phase(Block S142), after the relamination phase, to reposition the buildplatform 106 and the adhered prior layers of the build in preparationfor curing the subsequent layer of the build.

Thus, the system can execute the method S100 to distribute separationforces—between a photocured resin layer of a build and the separationmembrane 160—evenly across the resin layer by increasing fluid pressurein an interstitial region between the separation membrane 160 and thebuild window 110 while retracting the build platform 106 away from thebuild window 110. By distributing separation forces across thephotocured resin layer, the system may thus minimize peak forces at anyone location across the photocured resin layer, thereby reducingopportunity for damage or deformation of this layer or previouslyphotocured layers of the build. Additionally, the distribution ofseparation forces enables the use of resins exhibiting lower greenstrengths immediately after photocuring. Furthermore, by activelydrawing the separation membrane 160 back down across the flat, rigidbuild window 110, and removing substantially all fluid therebetween, thesystem can: rapidly prepare the build volume for a subsequent resinlayer; and consistently achieve a flat surface facing the build platform106 and exhibiting high parallelism to the build platform 106.Therefore, the system can execute the method S100 to produce resinlayers of consistent, controlled thickness and produce highly accuratebuilds with a high degree of repeatability across discrete builds and inless time.

Additionally, the system can execute the method S100 to achieve theforegoing results with minimal actuation of mechanical components,thereby increasing build speed, reducing system wear, and increasingrepeatability across individual resin layers and across builds.Furthermore, the system can also include a tray assembly 104 configuredto be engaged into and disengaged from a base assembly 102 (includingthe projection system 120, the build window 110, the build platform 106etc.) and configured to repeatably locate the separation membrane 160over the build window 110; a user can thus exchange tray assembliescontaining separation membranes of different materials and/orthicknesses in order to match the separation membrane 160 to theparticular chemical and physical properties of a photocurable resinselected for the next build and/or to the cross-sectional features orother geometric properties of the next build (e.g., thinner separationmembranes for builds with small features). The tray assembly 104 canadditionally or alternatively be disassembled to enable the user toexchange separation membranes matched to resin chemistries and/or buildgeometries for a build before rengaging the tray assembly 104 into thebase assembly 102. Furthermore, because the method S100 does notexclusively rely on an oxygenated layer over the surface of the buildwindow 110 or separation membrane 160 to achieve separation of a resinlayer, the system can execute the method S100 to additively manufacturebuilds with resins that are oxygen-inhibited or not oxygen stable.

3. Hardware

As shown in FIG. 2A, the system 100 includes two subassemblies ofelectromechanical components that, when engaged in an engagedconfiguration, can execute a “bottom-up” DLP process. Generally, thesystem 100 includes a base assembly 102 and a tray assembly 104. A usermay: assemble the tray assembly 104 by inserting a separation membrane160 into the tray structure 150; and engage the tray assembly 104 withthe base assembly 102 before the system 100 executes the method S100.The system 100 can then execute the method S100 via an imbeddedcomputational device running computer code (hereinafter the“controller”), which electronically actuates the build platform 106(e.g., via a linear actuation system) and controls the projection system120 and the pressure regulation system 190 to selectively cure volumesof resin and to separate these cured volumes of resin from the buildwindow 110 and separation membrane 160.

The system 100, in executing Blocks of the method S100, proceeds throughmultiple physical arrangements of the components in order to cure abuild (e.g., a set of physical, 3D objects) from the resin containedwithin the tray assembly 104. In a lamination phase, the system 100reduces the pressure (i.e. draws a vacuum/evacuates fluid from) in theinterstitial layer between the separation membrane 160 and the buildwindow 110, thereby fully laminating the separation membrane 160 againstthe build window 110 and preventing formation of bubbles or wrinklesthat may disrupt the reference surface for the system 100. During thelamination phase, the system 100 can execute Block S110 of the method inorder to photocure a selective volume of resin above the laminatedsurface of the separation membrane 160. Subsequent to completion ofBlock S110, the system 100 can execute a separation process including apressurization phase, a retraction phase, and a relamination phase,corresponding to Blocks S120, S130, and S140 respectively. In thepressurization phase the system 100 injects fluid into the interstitialregion, thereby generating separation between the separation membrane160 and the build window 110 in order to reduce adhesion forces (e.g.,Stefan adhesion, suction forces) between the newly cured layer of thebuild and the build window 110. In the retraction phase, the system 100actuates the build platform 106 upward and away from the build window110: to separate the separation membrane 160 from the build window 110;to peel the separation membrane 160 from the newly cured layer of thebuild; and to make space to photocure a successive layer of resin. Inthe relamination phase, the system 100 evacuates fluid from theinterstitial region in order to peel the separation membrane 160 fromthe newly cured layer of the build and to relaminate the separationmembrane 160 against the build window 110 in preparation for curing asuccessive layer of the build. Thus, the system 100 can repeat thisprocess cycle to cure successive layers of the resin, therebyconstructing a three-dimensional build.

3.1 Base Assembly

The system 100 includes a base assembly 102, which acts as the primaryassembly resembling a 3D printer. The base assembly 102 includes aprojection system 120, a window platform 132, a build window 110, afluid distribution port 140 and/or a fluid distribution channel 142, agasket system, a pressure regulation system 190, a tray seat 130, abuild platform 106, and a controller. The base assembly 102 can be afree-standing structure that may be placed on a level surface for bestprinting results. The free-standing structure of the base assembly 102links the aforementioned components in a calibrated arrangement thatensures consistent alignment between the projection system 120 and thebuild window 110 and parallelism between the reference plane of thebuild window 110, the surface of the retractable build platform 106, andthe focal plane(s) of the projection system 120. The structure of thebase assembly 102 can be manufactured from any rigid material that doesnot significantly deform under the weight of the base assembly 102 orthe stresses involved during repetitive build cycles.

The base assembly 102 can also include a build chamber, into which thetray assembly 104 may be loaded (e.g., via engagement with the tray seat130), and a hatch to provide access to this build chamber. The baseassembly 102 can further include systems configured to control theenvironment within the build chamber (e.g., such as an auxiliarypressure regulation system 190 and/or a set of heating elements).

3.1.1 Projection System

The projection system 120 is upward facing, is housed in the baseassembly 102, and can include one or more projectors configured toproject electromagnetic radiation in an emissive spectrum, which caninclude the ultraviolet (hereinafter “UV”), visible, or near infrared(hereinafter “NIR”) spectrum. The projection system can emitelectromagnetic radiation in one or more wavelength bands tuned to thechemical and physical properties of the resin and its specific curingprocess. For example, the projection system 120 (e.g., a digital UVprojector) can project electromagnetic radiation in an emissive spectrumof 300-nanometer to 450-nanometers. The projection system 120 iselectrically coupled to the controller; receives potentiallysoftware-modified frames corresponding to full or partial cross-sectionsof a three-dimensional model of the build; and projects electromagneticradiation through the build window 110 and separation membrane 160 inthe engaged configuration (and during the photocuring phase) toselectively photocure volumes of the resin according to build settingsand the received frames.

In one variation, the system 100 can include a projection system 120,which further includes a set of light sources, such as projectors orother electromagnetic emitting devices. In this variation, eachirradiation source of the projection system 120 can define a projectivearea within the build window 110 in order to maintain a higherresolution across the build window 110 via tiling or stitchingtechniques. Additionally or alternatively, each light source can definea separate emissive spectrum enabling the projection system 120 toproject electromagnetic radiation within multiple combinations ofspectral bands.

In one variation, the projection system 120 includes a UV or near-UVlaser and scans (e.g., as a raster) a laser beam across the build window110 according to frames received from the controller in order toselectively photocure a volume of resin located over the separationmembrane 160.

3.1.2 Window Platform

Generally, the window platform 132 extends upwards from a tray seat 130of the base assembly 102 and is configured to align within a trayaperture 152 of the tray assembly 104 when the system 100 is in theengaged configuration. The window platform 132 is a rigid structure thatencompasses the projection system 120 and defines an opening above theupward facing projection system 120 that is spanned by the build window110. The upper surface of the window platform 132 defines a horizontalreference plane which is coincident with the upper surface of the buildwindow 110 and the primary focal plane of the projection system 120. Thesystem 100 can include a window platform 132 of a shape that:corresponds to a shape of a tray aperture 152; enables engagement withthe separation membrane 160; and is configured to define fluiddistribution ports 140 and/or fluid distribution channels 142 around thebuild window 110 and within the interstitial region. For example, theupper surface of the window platform 132 can define a circular shape, arectangular shape, or any other shape depending on the desired shape ofthe tray aperture 152. In an additional example, the system 100 caninclude a window platform 132 of any size larger than the build regionof the system 100 and/or the dimensions of builds to be manufactured bythe system 100. The system 100 can include a window platform 132 withfilleted corners and edges around the upper surface of the windowplatform 132 to prevent tearing of the separation membrane 160 as it istensioned over the window platform 132.

The window platform 132 defines an opening that is spanned or partiallyspanned by the build window 110. Generally, the shape and size of theopening defined by the window platform 132 roughly corresponds with theshape and size of the upper surface of the build window 110 in order tomaximize utilization of the build region of the system 100.

3.1.3 Build Window

The build window 110 is mounted to the window platform 132 such that theupper surface of the build window 110 is approximately flush with theupper surface of the window platform 132 and further defines thehorizontal reference plane for builds manufactured in the system 100.The build window 110 is arranged above the projection system 120 andaligned with the projection area of the projection system 120 such thatthe focal plane of the projection system 120 coincides with the uppersurface of the separation membrane 160 laminated over the build window110. Generally, the build window 110 is substantially transparent (e.g.,exhibiting greater than 85% transmittance) to the emissive spectrum ofthe projection system and thus passes electromagnetic radiation outputby the projection system 120 into the resin above the build window 110and separation membrane 160. The build window 110 also functions as arigid support and reference surface for the separation membrane 160 anda layer of resin arranged thereover. The build window 110 is staticallymounted to a base assembly 102, via the window platform 132, that caninclude the projection system 120, the build platform 106, the fluiddistribution port 140, the pressure regulation system 190, and/or thebuild chamber to ensure repeatable, accurate alignment between the buildwindow 110 and the rest of the base assembly 102. The interface betweenthe rigid window platform 132 and the build window 110 is alsogas-impermeable such that a pressure gradient, such as 300 kilopascals,can be sustained across the build window 110.

The base assembly 102 can include a build window 110 manufactured from apane of transparent, rigid glass, such as amorphous/silicate orcrystalline/ceramic glass. In particular, the build window 110 can beboth transparent to ultraviolet (or other) light output by theprojection system 120 and can be substantially rigid, hard, andtemperature-stable to form a robust, flat reference surface thatsupports the separation membrane 160 and that may exhibit minimaldeflection or deformation during multiple build cycles, thereby yieldinghigh and consistent build quality.

In one variation, the base assembly 102 can include a build window 110that is transmissive to infrared (hereinafter “IR”) radiation such thata thermographic sensor positioned below the build window 110 canaccurately calculate the temperature of the resin during a during thephotocuring phase of the build cycle.

3.1.4 Fluid Distribution Ports

The base assembly 102 includes one or more fluid distribution ports 140configured to fluidically (i.e. pneumatically or hydraulically) couplethe pressure regulation system 190 to the interstitial region betweenthe separation membrane 160 and the build window 110, thereby enablingthe pressure regulation system 190 to inject and/or evacuate fluid fromthe interstitial region while the system 100 is in the engagedconfiguration. The fluid distribution ports 140 can therefore be locatedwithin a gasket system that forms a seal between the base assembly 102and the tray assembly 104 and, more specifically, between the buildwindow 110 and the separation membrane 160. Each fluid distribution port140 can define an opening that is fluidically coupled to the pressuredistribution system 100 to enable the system 100 to adjust the pressurewithin the interstitial region via the pressure distribution port byinjecting and/or evacuating fluid from the fluid distribution ports 140.In one implementation, the system 100 includes an inlet fluiddistribution port 140 and an outlet fluid distribution port 140, whichprovides an inlet for fluid entering the interstitial region and anoutlet for fluid evacuating from the interstitial region respectively.Alternatively, the base assembly 102 includes a single fluiddistribution port 140, which is configured with the pressure regulationsystem 190 as both an outlet and an inlet for fluid in the interstitialregion. In another implementation, the base assembly 102 can includeadditional fluid distribution ports 140 arranged throughout theinterstitial region in order to reduce asymmetrical fluid flow from oneside of the interstitial region to another.

3.1.5 Fluid Distribution Channel

In one variation, the base assembly 102 includes a fluid distributionchannel 142 intersecting the fluid distribution ports 140 and configuredto distribute fluid evenly throughout the interstitial region. Morespecifically, the base assembly 102 can include a fluid distributionchannel 142 configured to reduce asymmetrical fluid flow relative to thebuild window 110 and the separation membrane 160 by distributing fluidfrom a fluid distribution port 140 throughout the interstitial region.Thus, when fluid is injected into or evacuated from the interstitialregion, the entire region is pressurized and/or depressurizedsubstantially simultaneously, thereby preventing bubble formation in theseparation membrane 160 or uneven separation of the separation membrane160 from the build during the retraction and/or relamination phase.

In one implementation, the fluid distribution channel 142 is integratedwithin the window platform 132 supporting the build window 110 anddefines a channel inset into the upper surface of the rigid windowplatform 132. In this implementation, the fluid distribution channel 142is arranged circumferentially around the perimeter of the build window110 and intersects an inlet fluid distribution port 140 and an outletfluid distribution port 140 fluidly coupled to the pressure regulationsystem 190. Thus, the base assembly 102 can include a fluid distributionchannel 142 circumscribing the build window 110 and configured todistribute fluid evenly in the interstitial region.

However, the base assembly 102 can include a fluid distribution channel142 defining any path throughout the interstitial region that reducesasymmetrical fluid flow within the interstitial region.

3.1.6 Pressure Regulation System and Pressure Chambers

Generally, as shown in FIG. 7, the base assembly 102 can include apressure regulation system 190 configured to pressurize and/ordepressurize by injecting and/or evacuating fluid from the interstitialregion in accordance with the method S100. More specifically, the baseassembly 102 can include a pressure regulation system 190 that is:fluidically coupled to the fluid distribution port 140; configured toinject fluid into the interstitial region to separate the separationmembrane 160 from the build window 110 in the engaged configuration andduring a pressurization phase; and configured to evacuate fluid from theinterstitial region to laminate the separation membrane 160 to the buildwindow 110 in the engaged configuration and during a lamination phase.

The pressure regulation system 190 can include a pump (e.g., a diaphragmpump) and a set of electromechanical valves connected by a set of tubesto the fluid distribution ports 140. More specifically, the pressureregulation system 190 can include a pump fluidically coupled to a set oftwo electromechanical valves configured to actuate in response tocommands from the system 100 and direct fluid flow through the pump intothe interstitial region or out of the interstitial region based on acurrent phase of the build cycle.

In one implementation, the pressure regulation system 190 includes a setof electronically actuated valves configured to regulate flow between acompressed fluid supply line (e.g., a compressed air supply line in thebuilding housing the system) and a central vacuum line. The system 100can, therefore, be connected—such as via external ports—to thecompressed fluid supply line and the central vacuum line.

In another implementation, the pressure regulation system 190 includes acompressor system 100 (e.g., a centrifugal compressor) and an externalair port and is configured to: intake ambient air via the external airport; compress this ambient air; and inject this ambient air into theinterstitial region. The pressure regulation system 190 can alsoevacuate air from the interstitial region via the compressor and theexternal air port by running the compressor system 100 in reverse.Alternatively, the pressure regulation system 190 is fluidly coupled toa fluid reservoir (e.g., a tank containing an inert fluid). Thus, thesystem 100 can inject fluid from the fluid reservoir into theinterstitial region or evacuate this fluid into the fluid reservoir viathe pressure regulation system 190.

In yet another implementation, the base assembly 102 can include acompressor system 100 and/or a system 100 of electronically actuatedvalves configured to draw fluid from the pressurized build chamber(e.g., above the surface of the resin reservoir contained in the buildtray) in order to pressurize the interstitial region in thepressurization phase. Likewise, the system 100 can evacuate fluid fromthe interstitial region back into the build chamber during therelamination phase and/or the lamination phase. Thus, in thisimplementation, the system 100 can operate independently from externalsources of a working fluid for pressurization or depressurization of theinterstitial region.

Additionally or alternatively, the base assembly 102 can include asecond pressure regulation system 190 configured to control the pressureof the build chamber independent from the pressure of the interstitialregion. The system 100 can coordinate the first pressure regulationsystem 190 and the second pressure regulation system 190 to improveseparation (e.g., reduce separation forces and increase separationspeed) of the separation membrane 160 from the cured resin layer of thebuild.

The pressure regulation system 190 can maintain a maximum operatinginflation differential pressure up to or exceeding 300 kilopascals andcan pull a vacuum (e.g., a maximum operating deflation pressure) greaterthan 200 kilopascals. These pressures are sufficient to adequatelyseparate the separation membrane 160 from the build window 110 in thepressurization phase and to laminate the separation membrane 160 to thebuild window 110 in the lamination and/or the lamination phase. However,the pressure regulation system 190 can maintain alternative operatingdifferential pressures based on the volume of the interstitial regionand the force exerted on the interstitial region by the separationmembrane 160 due to the particular elasticity and thickness of theseparation membrane 160.

Additionally, the pressure regulation system 190 can include resin trapsand can be configured to purge these resin traps (via the actuation ofpurge valves) to remove resin from these resin traps when the pressureregulation system 190 is accidentally contaminated with resin (e.g., dueto spillage from the resin reservoir during engagement or failure of theseparation membrane 160 due to excessive wear). Alternatively, thepressure regulation system 190 can purge resin from the fluiddistribution ports 140 by pumping fluid out of the fluid distributionports 140 while the base assembly 102 is disengaged from the trayassembly 104.

3.1.7 Gas-Permeable Layer

Generally, as shown in FIG. 6, the base assembly 102 can include anintermediate gas-permeable layer 180 arranged over the surface of thebuild window 110 and between the build window 110 and the separationmembrane 160 when the system 100 is in the engaged configuration. Morespecifically, the base assembly 102 can include a gas-permeable layer180 that is: substantially transparent to electromagnetic radiationwithin the photo-initiating range; arranged over the upper surface ofthe build window 110; and configured to maintain a minimum interstitialvolume within the interstitial region between the build window 110 andthe separation membrane 160 in the engaged configuration. Thus, bymaintaining space between the separation membrane 160 and the buildwindow 110 in the engaged configuration, the gas-permeable layer 180reduces the incidence of bubbles between the separation membrane 160 andthe build window 110 during the lamination phase of the build cycle.Additionally, inclusion of the gas-permeable layer 180 can reduce oreliminate suction forces between the separation membrane 160 and thebuild window 110.

In one implementation, the base assembly 102 includes a gas-permeablelayer 180 that defines a gas-permeable grid or lattice structure overthe build window 110. In this implementation, the gas-permeable layer180 can be manufactured from a material that is substantiallytransparent (e.g., greater than 85% transmittance) and characterized bythe similar index of refraction as the build window 110 in order toreduce aberrations in the projection incident with the resin oppositethe separation membrane 160 during the photocuring process.

3.1.8 Tray Seat

The base assembly 102 can define a tray seat 130 around the base of thewindow platform 132 with a surface offset below the upper surface of thewindow platform 132 such that the window platform 132 protrudes upwardsfrom the center of the tray seat 130. The tray seat 130 defines asurface with a high degree of parallelism with the reference planedefined by the window platform 132. Additionally, the vertical offsetbetween the tray seat 130 and the reference plane can be calibratedand/or constructed with a low tolerance such that, when the trayassembly 104 is seated at the tray seat 130 of the base assembly 102 inthe engaged configuration, the separation membrane 160 is preciselypositioned relative to the build window 110. In one variation, thesystem 100 includes a tray seat 130 and tray assembly 104 tolerancestack that positions the separation membrane 160 slightly above (e.g.,less than 1 millimeter above) the build window 110 when there is 110pressure gradient across the separation membrane 160. In anothervariation, the system 100 defines a tray seat 130 and tray assembly 104tolerance stack that positions the upper surface of the window platform132 and/or build window 110 such that these surfaces protrude into thetensioned separation membrane 160 while the system 100 is in the engagedconfiguration, thereby automatically laminating the separation membrane160 against the build window 110.

The tray assembly 104 can define a set of registration features 154corresponding to complimentary reference features 134 arranged on thetray seat 130 of the base assembly 102. Therefore, in the engagedconfiguration, the registration features 154 can constrain the trayassembly 104 relative to the base assembly 102. In one implementation,the reference features 134 of the base assembly 102 and the registrationfeatures 154 of the tray assembly 104 are configured to kinematicallyalign the tray assembly 104 relative to the base assembly, therebymaintaining a precise offset between the separation membrane 160 and thebuild window 110 and/or preventing movement of the tray assembly 104relative to the base assembly 102 during the build cycle. In anotherimplementation, the base assembly 102 can include imbedded magneticfeatures underneath the tray seat 130 in order to bias the tray assembly104 downward onto the reference features 134 of the tray seat 130.Alternatively, the base assembly 102 can include a set of mechanicalclamps or screws in order to seat the tray assembly 104 at the tray seat130 of the base assembly 102.

3.1.9 Reference Features

Generally, the reference features 134 defined by the tray seat 130 areconfigured to correspond to matching features in the tray assembly 104and to thus align the tray assembly 104 with the base assembly 102. Morespecifically, the base assembly 102 can define positive referencefeatures 134 or negative reference features 134 on the tray seat 130.Alternatively, the base assembly 102 can include reference features 134that are separate components configured to install onto the tray seat130. In combination with a biasing force, such as a magnetic forcebetween corresponding magnetic features in the base assembly 102 andtray assembly 104, mechanically applied force securing the tray assembly104 to the base assembly 102, and/or the force of gravity pulling thetray assembly 104 downward onto the base assembly 102, the referencefeatures 134 kinematically constrain the tray assembly 104 relative tothe base assembly 102 in all six degrees-of-freedom. Thus, correspondingreference features 134 defined in the tray seat 130 and in the trayassembly 104 can repeatably and accurately align the tray assembly 104with the base assembly 102 when the tray assembly 104 is engaged withthe base assembly 102.

3.1.10 Magnetic Locking Mechanism

Generally, the system 100 can include a set of magnets imbedded withinthe base assembly 102 below the tray seat 130 and a correspondingmagnetic material (e.g., a ferromagnetic substance) imbedded within thetray assembly 104, thereby biasing the tray assembly 104 toward the trayseat 130. More specifically, the base assembly 102 can include amagnetic lock arranged within the tray seat 130; and the tray assembly104 can include a magnetic registration feature 154 configured tomagnetically engage with the magnetic lock in the engaged configuration.

In one implementation, the base assembly 102 can include anelectromagnetic lock as the magnetic lock such that the system 100 canactively engage and/or disengage the tray assembly 104 from the baseassembly 102 via an electrical current. Thus, the base assembly 102 caninclude an electromagnetic lock configured to: magnetically engage withthe magnetic registration feature 154 in the engaged configuration; andmagnetically disengage with the magnetic registration feature 154 in adisengaged configuration.

3.1.11 Build Platform

Generally, the base assembly 102 also includes a vertically mobile buildplatform 106 to which a first layer of the build adheres and from whichthe build is suspended toward the build window 110 during the buildcycle. More specifically, the base assembly 102 can include a buildplatform 106 defining a planar surface opposite and substantiallyparallel to the upper surface of the build window 110; and a linearactuation system (including a single linear actuator or multiple timedlinear actuators) configured to vertically translate the build platform106 relative to the build window 110. In one implementation, the system100 can include a build platform 106 defining negative features, such aschannels or through holes to improve the flow of resin out from underthe build platform 106 during advancement of the build platform 106 intothe resin reservoir and to facilitate the removal of the build from thebuild platform 106 after completion of the build.

The build platform 106 is a vertically actuating surface opposite thebuild window 110. The system 100 can include a linear actuation system(with increments as small as 0.1 microns) mechanically coupled to thebuild platform 106. Additionally, during actuation of the linearactuation system, the controller: can track forces applied by the linearactuation system to the build platform 106 (e.g., based on a currentdraw of the linear actuation system or by sampling a force sensor orstrain gauge coupled to the build platform 106); and implementclosed-loop techniques to control movement of the linear actuationsystem in order to achieve a particular distribution of separationforces between the newly cured layer of the build and the separationmembrane 160 (e.g., to sweep this separation force along a predefinedforce profile once per layer). Thus, during the build cycle the linearactuation system lowers the build platform 106 to specific heights abovethe separation membrane 160 such that photocured resin adheres to thebuild surface of the build platform 106 facing the window. As the system100 selectively cures successive layers of the build according to Blocksof the method S100, the system 100 can retract the build platform 106upward by a first distance in order to separate the current layer of thebuild from the separation membrane 160 and then advance the buildplatform 106 downward—by a second distance less than or equal to thefirst distance—in preparation for curing a successive layer of thebuild.

3.1.12 Controller

The base assembly 102 of the system 100 can include a controller thatcontrols the electromechanical components of the system 100. Generally,the controller is an imbedded computer system that sends instructions tothe projection system 120, the pressure regulation system 190, and thelinear actuation system coupled to the build platform 106, to executethe method S100. In one implementation, the controller controls andreceives instructions from a user interface, which can be a touchscreenor a set of buttons, switches, nobs, etc. Alternatively, the controllercan communicate with and receive instructions from an externalcomputational device. In another implementation, the controller isconnected to a network, such as the internet, and is configured toreceive instructions over the network. Additionally, the controller cansend commands, in the form of digital and/or analog electrical signals,in order to actuate various electromechanical components of the systemsuch as the magnetic locking mechanism, a door hatch release to thebuild chamber, the purge valves, and/or lighting elements within thebuild chamber. Furthermore, the controller can receive data from sensorsintegrated with the system 100 and execute feedback control algorithmsbased on these data in order to modify the function of the projectionsystem 120, the pressure regulation system 190, and/or the linearactuation system.

3.2 Tray Assembly

As shown in FIG. 2B, the system 100 includes a tray assembly 104 (i.e. abuild tray) which further includes: a tray structure 150 (which candefine an upper member 155 and a lower member 156), a separationmembrane 160, a set of tensioning gaskets 162, and/or a resin-sealinggasket 164. The tray assembly 104 is configured to engage (e.g.,kinematically mount to) the base assembly 102 over the window platform132 via corresponding registration features 154 arranged on theunderside of the tray structure 150 and reference features 134 on thetray seat 130. Generally, the tray assembly 104 contains the resinreservoir during a build cycle and positions and maintains the tensionin the separation membrane 160 over the window platform 132, buildwindow 110, and/or fluid distribution ports 140. More specifically, thetray assembly 104 can include a tray structure 150 that defines an uppermember 155 and a lower member 156, which are fastened together via a setof fasteners with the separation membrane 160 in between the uppermember 155 and the lower member 156. Thus, the tray structure 150functions to position the separation membrane 160 so that it isconfigured to: laminate across the upper surface of the build window 110in response to an evacuation of fluid, via the fluid distribution port140, from an interstitial region between the base assembly 102 and thetray assembly 104 in the engaged configuration; and configured toseparate from the build window 110 in response to injection of fluid,via the fluid distribution port 140, into the interstitial region.

In one implementation, the base assembly 102 includes a sealed buildchamber that encloses the tray assembly 104 and sealed. Additionally,the build chamber can be filled with an inert fluid, such as to enableuse of reactive (e.g., reactive with oxygen) resin chemistries in thesystem 100. In one implementation, the build chamber is integrated withthe upper member 155 of the tray structure 150. In this implementation,the resin can be injected into the inner volume of the assemblyincluding the build tray and the build chamber via an injection portsuch that the resin is not exposed to the atmosphere at any point whilebeing loaded into the tray assembly 104.

3.2.1 Tray Structure

Generally, the tray structure 150: defines a tray aperture 152 spannedby the separation membrane 160 and circumscribing the build window 110;defines registration features 154 configured to engage with thereference features 134 of the tray seat 130; and defines an interiorvolume for containing the resin reservoir. The tray structure 150 can beconstructed from a rigid, non-reactive, temperature stable solidmaterial, such as aluminum or another metal or metal alloy. In oneimplementation, the tray structure 150 is constructed from milledaluminum. Additionally, the tray assembly 104 can be a member of a setof tray assemblies associated with the system 100, each tray assembly104 in the set of tray assemblies including a tray structure 150 of adifferent shape or size in order to accommodate a wider variety of buildsizes and shapes. In one implementation, the tray structure 150 includesan upper member 155 and a lower member 156 configured to fasten to eachother via a set of fasteners. Thus, during assembly of the trayassembly, a user may arrange the separation membrane 160 between thelower member 156 and the upper member 155, thereby repeatably locatingthe separation membrane 160 relative to the tray seat 130 in the engagedconfiguration.

Generally, the upper member 155 of the build tray defines the volumeoccupied by the resin during the build cycle and the region within whichthe system 100 can selectively photocure this resin into the build viaexecution of a series of build cycles. The upper member 155 also definesan tray aperture 152 that corresponds to the window platform 132 suchthat the upper member 155 can be lowered over the window platform 132 ofthe base assembly 102. The tray aperture 152 in the upper member 155 isspanned by the separation membrane 160 thereby enclosing the volumedefined by the upper member 155 from the bottom. Thus, the tray assembly104 when fully assembled defines an interior volume above the separationmembrane 160 tensioned across the tray aperture 152, the interior volumeconfigured to contain a reservoir of resin.

In one implementation, an inner surface of the build region is roundedto reduce stress concentrations in the separation membrane 160. In oneimplementation, the upper member 155 of the build tray defines a roundedrectangular build region. Additionally, the upper member 155 can definean inner surface that extends upward and perpendicular to the buildwindow 110. The inner surface then expands upward and outward in aconical shape, wherein the vertical cross section of the conical innersurface has dimensions proportionally similar to the verticalcross-section of the perpendicular inner surface. Thus, theperpendicular and conical sections of the inner surface define a volumeconfigured to contain the resin reservoir. However, the upper member 155of the build tray can define any rounded internal volume. Additionally,the upper member 155 can include integrated heating and/or coolingelements. The system 100 can activate the heating and/or coolingelements to adjust the temperature of the resin within the build tray tonear an optimal temperature for the photocuring reaction of the resin.

The lower member 156 defines a shape consistent with the inner surfaceof the upper member 155 and can define corresponding features to thereference features 134 in the tray seat 130 of the base assembly 102. Inone implementation, the base assembly 102 and/or the lower member 156contain magnets (i.e. magnetic registration features 154), whichkinematically align the lower member 156, and therefore the trayassembly 104, to the base assembly 102 by biasing the lower member 156against the reference features 134 in the base assembly 102. The lowermember 156 also defines holes such that fasteners, such as screws orbolts, passing through the holes can insert into corresponding holes inthe upper member 155. Alternatively, the system can include fastenersthat are directly integrated with either the upper member 155 and/or thelower member 156 and the system can include an upper member 155 and alower member 156 configured to slot directly into the opposite member ofthe tray structure 150.

3.2.2 Separation Membrane

The separation membrane 160 can include a transparent, thin, andflexible film or sheet characterized by low adhesion to photocuringresins. The separation membrane 160 is manufactured at sizes specific toparticular tray assemblies 104 and with holes aligned with tensioningposts 159 extending from either the upper member 155 or the lower member156 of the build tray. Thus, the separation membrane 160 is positionedbetween the upper member 155 and the lower member 156 of the build traysuch that the tensioning posts 159 extend from one member of the traystructure 150, through a hole, slot, or perforation in the separationmembrane 160, and into corresponding negative features in the oppositemember of the tray structure 150. Additionally or alternatively, theseparation membrane 160 can define a set of holes and/or slots such thatthere is an interference fit between the separation membrane 160 and theset of tensioning posts 159, thereby preloading (i.e. automaticallytensioning) the separation membrane 160 with a tensile stress.

Thus, the tray assembly 104 can include an upper member 155 and a lowermember 156 with interlocking features and a separation membrane 160perforated in an interference fit with these interlocking features.Therefore, the geometry of the tensioning posts 159 relative to thecorresponding perforations in the separation membrane 160 functions toautomatically tension the separation membrane 160 across the trayaperture 152 defined by the tray structure 150. For example, the uppermember 155 of the tray structure 150 can define milled positive featuresincluding the tensioning posts 159 corresponding to milled negativefeatures in the lower member 156 such that the negative features of thelower member 156 fit over the positive features of the upper member 155.In this example, the separation membrane 160 defines perforationscorresponding to the positive features of the upper member 155 in aninterference fit. In this implementation, the tray assembly 104 canfurther include separate fasteners—such as magnets, clasps, latches,and/or screws—to fasten the lower member 156 to the upper member 155.

However, the separation membrane 160 can be tensioned across the trayaperture 152 defined by the tray structure 150 in any other way (e.g.,via direct bonding to the tray structure 150 or via another fasteningconfiguration).

Thus, in one implementation, the tray assembly 104 can include: an uppermember 155 defining a set of positive features including a set oftensioning posts 159; a lower member 156 defining a set of negativefeatures configured to engage with the set of positive features; aseparation membrane 160 arranged between the upper member 155 and thelower member 156 and defining a third set of perforations outwardlyoffset from the set of tensioning posts in an interference fit betweenthe separation membrane 160 and the set of tensioning posts 159tensioning the separation membrane 160 via the interference fit.

3.2.3 Separation Membrane Selection

As described above, the system 100 can include an interchangeableseparation membrane 160. Therefore, a user may select different trayassemblies containing various separation membranes and tray structureconfigurations and/or install separation membranes of different types inone tray assembly 104 based on various factors, such as: the geometry(e.g., feature sizes) of a build queued for manufacture by the system100; characteristics of the resin chemistry selected for the build and acorresponding photocuring process; the target green strength of theselected resin; and/or cumulative wear or degradation of the separationmembrane 160. The separation membrane 160 is replaceable by removing thefasteners in the tray assembly 104 and separating the upper member 155and the lower member 156 of the build tray from the separation membrane160. After the separation membrane 160 is removed a new separationmembrane 160 can be placed over the tensioning posts 159, therebysecuring the new separation membrane 160 between the upper member 155and the lower member 156 of the build tray.

Because the separation membrane 160 is exchangeable within the buildtray, the system 100 can include multiple types of separation membraneswith varying sizes, thicknesses, tensions, permeabilities, elasticitiesand/or materials, which may be selected by a user or specified by thesystem 100 based on the resin loaded into the interchangeable trayassembly 104. In one implementation, the separation membrane 160 isconstructed from copolymerized tetrafluoroethylene (hereinafter “TFE”)and has a thickness less than one millimeter, and low fluidpermeability. Alternatively, the membrane is constructed from2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole (hereinafter “TFE-AF”)and has high oxygen permeability such that a layer of the resin can beoxygenated.

In one implementation, the system 100 includes an oxygen-permeableseparation membrane 160 to allow oxygen to saturate a layer above theseparation membrane 160 within the resin. In resins withoxygen-inhibited chemistries, the oxygen saturated layer can thereforeprevent the resin from photocuring against (and adhering to) theseparation membrane 160 or the build window 110 to a certain depthbeyond the separation membrane 160. In this implementation, theseparation membrane 160 can be constructed from TFE-AF. Additionally,the system 100 can include a separation membrane 160 of a greaterthickness and/or stiffness, an increased offset between the separationmembrane 160 and the build window 110, and/or execute a decreased peakinflation pressure during Block S120 (e.g., so that the separation candiffuse oxygen into the resin without substantially deflecting). In oneimplementation, the pressure applied to the interstitial region betweenthe build window 110 and the separation membrane 160 is matched to theatmospheric pressure at the upper surface of the separation membrane 160such that the pressure gradient across the separation membrane 160 isnegligible.

When the system 100 is manufacturing a build with relatively delicatefeatures, a thinner membrane (e.g., between 20 microns and 5o micronsthick) can be inserted into the tray assembly 104. The thinner membranemay have greater elasticity and therefore may impart a smaller magnitudeof force as it is pulled away from the layer features during each buildcycle. However, thinner separation membranes 160 may wear more rapidly(e.g., over fewer build cycles) than thicker separation membranes andthus may require replacement at a higher frequency. Conversely, athicker separation membrane 160 (e.g., up to 150 microns thick) may beloaded into the tray assembly 104 when builds defining more robustgeometries are queued at the system 100, since a thicker separationmembrane 160 may be more resistant to cumulative wear, may be replacedless often, and may withstand greater forces necessary to separatelarger resin features from the build window 110. For example, a user mayload a thin separation membrane 160 into the build tray when a resinwith low green strength is selected for a next build in the system 100,since this thinner separation membrane 160 may apply lower forces tolayers of this cured resin. However, the user may also load a thickerseparation membrane 160 into the build tray when a resin with highergreen strength is selected for a next build in the system 100, sincethis thicker separation membrane 160 may be more robust and/or may beinflated faster than a thin separation membrane 160, thereby enablingshorter separation periods between layers of the build. Thus, a firsttray assembly 104 can include a first separation membrane 160 defining afirst thickness between 50 and 200 microns and a second tray assembly104 can include: the tray structure 150 of the first tray assembly 104;and a second separation membrane 160, defining a thickness less than 5omicrons, tensioned across the tray aperture 152 defined by the traystructure 150, configured to configured to laminate across the uppersurface of the build window 110 in response to an evacuation of fluid,via the fluid distribution port 140, from an interstitial region betweenthe base assembly 102 and the tray assembly 104 in the engagedconfiguration, and configured to separate from the build window 110 inresponse to injection of fluid, via the fluid distribution port 140,into the interstitial region.

Additionally, the user may exchange separation membranes 160 accordingto the chemistry of the resin or the photocuring reaction of the resinin order to improve release characteristics of the resin. Although TFEis generally chemically stable, separation membranes 160 of alternativecompositions can be included in the system 100 when manufacturing withan especially reactive resin composition or resins that exhibitespecially exothermic photocuring reactions. In alternativeimplementations, tray assembly 104 can include a separation membrane 160manufactured from semi-crystalline perfluoroalkoxy alkane (i.e. PFA) orfluorinated ethylene propylene (i.e. FEP). In one implementation, theseparation membrane 160 is coated with a transparent super-hydrophobicnanocoating to prevent adhesion between the separation membrane 160 andthe build in its green state.

Furthermore, the system 100 can be supplied with a set of separationmembranes 160 characterized by different oxygen or gas permeabilities.For example, a separation membrane 160 of TFE or PFA may be relativelyimpermeable to oxygen (e.g., at thicknesses greater than 50 microns) andtherefore may be loaded into the tray assembly 104 when the system 100is photocuring an oxygen-sensitive resin such as a thiol resin or apolyolefin resin. Thus, the tray assembly 104 can include a separationmembrane 160 manufactured from an oxygen-impermeable film. Because thesystem loo can control the oxygen concentration in the resin reservoir(via an inert environment in the build chamber and an oxygen-impermeablemembrane), the system loo can photocure resins containing lowerproportions of photoinitiator, thereby improving photocuring speed,cross-link density, and green strength of builds constructed from theseresins.

Alternatively, the user may load a separation membrane 160 of TFE-AFinto the build tray in order to intentionally create an oxygen richregion in the resin reservoir to inhibit photocuring of the resinproximal to the separation membrane 160, thereby further improvingseparation from the separation membrane 160 at the expense of limitingthe variety of resin chemistries that are compatible with the separationmembrane 160. Thus, the tray assembly 104 can include a separationmembrane 160 manufactured from a gas-permeable film.

The tray assembly 104 can further include a separation membrane 160characterized by a high heat deflection, continuous use, or glasstransition temperature, thereby enabling the separation membrane 160 toresist higher reaction temperatures (e.g., up to 100 degrees Celsius)typical of certain resin chemistries. Thus, the tray assembly 104 caninclude a separation membrane 160: characterized by a heat deflectiontemperature greater than 100 degrees Celsius; and chemically inert tothe resin at a temperature of less than 100 degrees Celsius. However,the system can include a separation membranes 160 characterized by heatdeflection temperature less than the reaction temperature of thephotocurable resin at the expense of an increased rate of wear.

3.2.4 Tensioning Gaskets

In one implementation, the upper member 155 and the lower member 156include a set of rubber or rubberized plastic gaskets arranged aroundeach tensioning post 159 to distribute tensile force applied to theseparation membrane 160 over a larger area, thereby preventing excessivelateral movement/shifting or tearing of the separation membrane 160while under tension. The tensioning gaskets 162 effectively sandwich theseparation membrane 160 to bear the load of the tension in the membraneacross the entire area of the gasket. In addition, the tray assembly 104can include tensioning gaskets 120 configured to achieve a particulardistribution (e.g., an even distribution) of tensile forces across themembrane and a particular inflationary profile or behavior of theseparation membrane 160 (e.g., similar separation of the membraneindependent of location within the build region). Thus, the tensioninggaskets 162 can be arranged on the bottom surface of the upper member155 and/or the upper surface of the lower member 156 around the holesdefined for the tensioning posts 159 in the upper member 155 and thelower member 156.

3.2.5 Resin-Sealing Gasket

The system 100 can also include a resin-sealing gasket 164 arrangedalong the edge of the tray aperture 152 of the upper member 155 of thebuild tray. Generally, the resin-sealing gasket 164 prevents resiningress between the upper member 155 of the build tray and theseparation membrane 160. Thus, when the tray assembly 104 is loweredover and around the window platform 132, the separation membrane 160 istensioned and pulled upward by the window platform 132 protrudingthrough the inner opening of the build tray spanned by the separationmembrane 160. The separation membrane 160 is thus biased against theresin-sealing gasket 164 on the edge of the interior opening of theupper member 155 of the build tray creating a seal against resin held inthe build tray. Additionally, the resin-sealing gasket 164 can preventexcess shear stress from tearing the separation membrane 160 when itcomes into contact with the interior edge of the upper member 155 of thebuild tray.

In implementations where the separation membrane 160 is not pulledupward by a protruding window platform 132 in the engaged configuration(e.g., in implementations where the separation membrane 160 ispositioned less than one millimeter above the build window 110 in theengaged configuration when there is no pressure gradient across theseparation membrane 160), the tray assembly 104 can include a set ofresin-sealing gaskets 164 circumscribing the tray aperture 152 inbetween the separation membrane 160 and the upper member 155 of the traystructure 150.

3.3 Inter-Assembly Gasket Configurations

Generally, the system 100 can define an inter-assembly gasketconfiguration in order to fluidically isolate (e.g., for a maximumoperating pressure such as 300 kilopascals) the interstitial region fromthe build chamber and from external ambient environment in order toenable precise control of the pressure within the interstitial regionvia the pressure regulation system 190. Because the interstitial regionis enclosed during engagement of the tray assembly 104 with the baseassembly 102, the inter-assembly gasket configuration can includegaskets integrated with the tray assembly 104, the base assembly 102,and/or independent gasket components therebetween.

3.3.1 Active Lamination Gasket Variation

In an active lamination gasket variation, shown in FIGS. 4A and 4B, thesystem 100 includes a gasket integrated with the lower member 156 of thetray assembly 104 circumscribing the bottom edge of the tray aperture152 defined by the lower member 156 of the tray assembly 104 andconfigured to seal (i.e. within the maximum operating pressure of thesystem) against the base of the window platform 132 and/or the tray seat130 in the engaged configuration. Additionally, as shown in FIG. 4A,when the system 100 is in the engaged configuration and while there isno pressure gradient across the separation membrane 160, the separationmembrane 160 is suspended by the tray structure 150 offset from (bygreater than 50 microns) and parallel the surface of the build window110. Thus, when the pressure regulation system 190 evacuates fluid fromthe interstitial region (and, therefore, induces a negative pressuregradient across the separation membrane 160) the separation membrane 160laminates against the upper surface of the build window 110 as shown inFIG. 4B. More specifically, the system 100 can include an interfacegasket 172: arranged between a lower surface of the tray structure 150and a base of a window platform 132 supporting the build window 110 inthe engaged configuration; circumscribing the tray aperture 152, thefluid distribution port 140, and the build window 110 in the engagedconfiguration; and configured to seal fluid within the interstitialregion up to a maximum differential pressure greater than a maximumoperating pressure. Additionally, in this implementation, the system 100includes a tray assembly 104 which further includes the separationmembrane 160 tensioned across the tray aperture 152 above andsubstantially parallel to the build window 110 in the engagedconfiguration.

In the active lamination gasket variant, the positioning of theseparation membrane 160 offset (e.g., by greater than 50 microns) abovethe build window 110 reduces the incidence of bubble formation betweenthe separation membrane 160 and the build window 110 during therelamination phase because, as the system 100 pulls a vacuum across theseparation membrane 160 during the relamination phase, the volume of theinterstitial region decreases pulling to separation membrane 160 towardthe build window 110 from the center of the membrane. Therefore, theseparation membrane 160 laminates against the build window 110 from thecenter outwards, thereby preventing bubble formation during thisrelamination.

Additionally, in this variation, the base assembly 102 can include oneor more fluid distribution ports 140 that are arranged anywhere withinthe tray assembly 104 and the base assembly 102. In one implementation,the fluid distribution port 140 is arranged on the base of the windowplatform 132, thereby facilitating the even distribution of air aroundthe window platform 132.

In one implementation, the tray assembly 104 can include a sealinggasket arranged between the lower member 156 of the tray structure 150and the separation membrane 160 and circumscribing the tray aperture 152defined by the lower member 156 in order to prevent egress of fluid fromthe interstitial region during the pressurization phase of the buildcycle.

3.3.2 Passive Lamination Gasket Variation

In a passive lamination gasket variation, shown in FIGS. 5A and 5B, thesystem 100 includes an interstitial gasket 170 circumscribing the edgeof the window platform 132, which is configured to protrude through thetray aperture 152 defined by the tray assembly 104 such that theseparation membrane 160 is tensioned over the surface of the windowplatform 132 and creates a seal with the interstitial gasket 170 in theengaged configuration. Therefore, in this variation, the system 100defines an interstitial region that includes only the volume of fluidbetween the separation membrane 160 and the build window 110 (as opposedto also including fluid between the tray assembly 104 and the baseassembly 102). Additionally, in this variation, the system 100 caninclude a fluid distribution port 140 arranged on the surface of thewindow platform 132 proximal to the build window 110, thereby enablingthe pressure regulation system 190 to inject and/or evacuate fluid fromthis more localized interstitial region, as shown in FIG. 5B. As shownin FIG. 5A, the separation membrane 160 is laminated across the buildwindow 110 without a negative pressure gradient between the interstitialregion and the build chamber. Alternatively, in this variation, thesystem 100 can include a fluid distribution port 140 inset into thewindow platform proximal to a raised build window defining an uppersurface coincident with the edge of the window.

More specifically, the base assembly 102 can include the build window110 configured to protrude through the tray aperture 152 against theseparation membrane 160 in the engaged configuration. Additionally, thebase assembly 102 can include an interstitial gasket 17o: circumscribingthe fluid distribution port 140 and the build window 110; configured tocontact the separation membrane 160 in the engaged configuration; andconfigured to seal fluid within the interstitial region up to a maximumdifferential pressure greater than a maximum operating pressure.

The interstitial gasket 170 can be manufactured from rubber orrubberized plastic that can form a seal with the tensioned separationmembrane 160. Like the upper surface of the build window 110, the uppersurface of the interstitial gasket 170 is flush with the upper surfaceof the window platform 132 and is coincident with the horizontalreference plane defined by the window platform 132. In oneimplementation, the interstitial gasket 170 can form a seal with thetensioned separation membrane 160, when the tray assembly 104 is engagedwith the base assembly 102, that can withstand a pressure gradient of300 kilopascals.

In one implementation of this passive lamination variation, the system100 can include a window platform 132, which is configured to protrudethrough the tray aperture 152 defined by the tray assembly 104 such thatthe separation membrane 160 is tensioned over the surface of the windowplatform 132 and creates a seal directly with the edge of the windowplatform 132 in the engaged configuration. This implementation obviatesthe need for the interstitial gasket 170 on the edge by creating adirect seal against the material of the window platform 132.

4. Engagement and Initialization

As shown in FIG. 2B, before the system 100 executes the method S100, theuser may fasten the separation membrane 160 between the lower member 156and upper member 155. Once the separation membrane 160 is fastenedbetween the upper member 155 and lower member 156 of the build tray, theuser may lower the tray assembly 104 over the upper surface of thewindow platform 132 and the build window 110. As shown in FIGS. 3A and3B, the tray then kinematically aligns with the reference features 134of the base assembly 102, thereby engaging with the base assembly 102.In the passive lamination variation, when the tray assembly 104 and thebase assembly 102 are engaged the separation membrane 160 is tensionedflush against the surface of the build window 110 and covers the fluiddistribution channel 142. In this variation, the separation membrane 160also forms a fluid-impermeable seal (within the maximum operatingpressure of the system) against an interstitial gasket 170 arrangedalong the edge of the window platform 132 or with the edge of the windowplatform 132 itself. In the active lamination gasket variation of thesystem, the separation membrane 160 is positioned just above the buildwindow 110 upon kinematic alignment of the tray assembly 104 with thetray seat 130 of the base assembly 102.

Before or after the tray assembly 104 is engaged with the base assembly102, resin is loaded into the volume defined by the upper member 155 ofthe build tray and the separation membrane 160. If the resin is notsensitive to oxygen and/or ambient air, the resin may be poured directlyinto the build tray. However, if the resin is sensitive to oxygen,humidity, and/or ambient air, the resin can be injected into a trayassembly 104 through a sealed port in a sealed build chamber after thebuild chamber has been filled with an inert fluid.

Thus, after loading is complete, the build volume defined by the innersurface of the build tray is at least partially occupied by a volume ofresin. The resin is in contact with the upper surface of the separationmembrane 160 and the inner surface of the upper member of the trayassembly 104. However, the resin does not come into contact with thebuild window 110 underneath the separation membrane 160.

5. Build Cycle

Generally, as shown in FIG. 1 and referenced above, the system 100executes Blocks S110, S120, S130, and S140, to: selectively photocure avolume of resin corresponding to a layer of a build; separate theseparation membrane 160 from the build window 110, and also the newlycured layer of the build from the separation membrane 160; andreposition the separation membrane 160 and build platform 106 (adheredto the first layer) in preparation for photocuring a subsequent layer.More specifically, the system 100: cures a first layer of the build;inflates the interstitial region between the separation membrane 160 andthe build window 110; retracts (e.g., raises) the build platform 106vertically upward away from the build window 110; and depressurizes theregion between the separation membrane 160 and the build window 110 inorder to peel the separation membrane 160 away from the first layer ofthe build and draw the separation membrane 160 down onto and flatagainst the build window 110. In one implementation, the system 100 canalso advance/reposition the build platform 106 (and the adhered firstlayer of the build) such that the lower surface of the most recentlycured layer of the build is offset from the surface of the separationmembrane 160 (that is laminated across the build window 110) by adistance equal to a desired layer thickness of the next layer as shownin Block S142.

Additionally, as is further described below, the system 100 can executeBlocks S120, S130, S140 and/or S142 in a synchronized sequence—such asduring discrete or (partially-) overlapping time periods—in order torepeatably separate build, including the newly cured layer of the buildfrom the separation membrane 160 and with minimal damage or deformationof the build in its green state.

Furthermore, some Blocks of the method S100 may be described withreference to a “first layer” of the build. However any of the Blocks ofthe method S100 are also applicable to subsequent layers of the build.

5.1 Build Chamber and Resin Reservoir Conditions

In one implementation, prior to executing Block S110, the system 100 canadjust the temperature and pressure of the gas within the build chamber,and/or adjust the temperature of the resin in the resin reservoir.

For example, the system 100 can heat the resin in the reservoir (e.g.,via heating elements integrated with the tray structure 150 or under thebuild window 110) in order to decrease the viscosity of the resin orcause a phase change in the resin from solid to liquid, therebyimproving print speeds and printability of the resin. More specifically,the system 100 can access a target temperature for the resin based on atemperature-viscosity curve corresponding to the resin and a targetviscosity for the resin; and heat the resin to the target temperature.

In another example, the system 100 can increase the temperature of thegas environment within the build chamber to match the target temperaturefor the resin in order to prevent convective currents from formingwithin the build chamber and therefore increasing evaporation rates ofchemical components of the resin (which may degrade the performance ofthe resin). The system 100 can also heat the gas environment within thebuild chamber to prevent solidifying of resin surrounding a build in itsgreen state after being retracted out of a heated resin bath, inimplementations where the system maintains the resin in a liquid phasedue to the elevated temperature of the resin reservoir. Additionally,the system 100 can control the temperature of the build chamber toprevent deformation of the build in its green state when exposed todifferential pressures between the resin reservoir and the gasenvironment within the build chamber.

Furthermore, the system 100 can increase the pressure within the buildchamber to reduce the evaporation rate of chemical components of theresin. In yet another example, the system 100 can introduce an inertfluid environment within the build chamber when the system 100 isphotocuring especially reactive resin chemistries (e.g.,oxygen-sensitive resin chemistries).

5.2 Lamination

As shown in FIG. 8, while selectively curing a current layer of resin inBlock S110, the system 100 minimizes the interstitial space between thebuild window no and the separation membrane 160 in order to repeatablymaximize flatness and planarity of the outer surface of the separationmembrane 160 in Block S102. In one implementation, prior to executingBlock S110, the controller can trigger the pressure regulation system190 to draw a vacuum on this interstitial region in order to flatten theseparation membrane 160 across the build window 110. The pressureregulation system 190 can also continue to draw vacuum on theinterstitial space between the build window 110 and the separationmembrane 160—via the fluid distribution port 140—in order to maintaincontact between the build window 110 and the separation membrane 160during Block S110. By drawing vacuum on this interstitial space prior toBlock S110, the system 100 can thus remove bubbles from between thebuild window 110 and the separation membrane 160 and ensure that theseparation membrane 160 is laminated flush against the surface of thebuild window 110. Thus, the system 100 can: concurrently draw a vacuumin the interstitial region to maintain lamination of the separationmembrane 160 to the build window 110 while photocuring the first volumeof liquid resin in Block S110; and concurrently draw a vacuum in theinterstitial region to maintain lamination of the separation membrane160 to the build window 110 while photocuring the second volume ofliquid resin in Block S150.

Alternatively, the system 100 can achieve lamination via engagementbetween the tray assembly 104 and the base assembly 102, as describedabove and shown in FIGS. 5A and 5B. Thus, the system 100 can: photocurethe first volume of resin to form the first layer of the build at theupper surface of the separation membrane 160 laminated over the buildwindow 110 via engagement of a tray assembly 104 around the windowplatform 132, the separation membrane 160 tensioned over the buildwindow 110 by the tray assembly 104 in Block S110; and photocure thesecond volume of resin to form the second layer of the build at theupper surface of the separation membrane 160 laminated over the buildwindow 110 via engagement of the tray assembly 104 around the windowplatform 132, the separation membrane 160 tensioned over the buildwindow 110 by the tray assembly 104 in Block S150.

5.3 Initial Photocuring Phase

In Block S110, the system 100 selectively photocures a first volume ofresin to form a first layer of a build (e.g., corresponding to a firstcross section of the build), wherein the build adheres to the buildplatform 106 opposite the separation membrane 160. Generally, once thebuild platform 106 has lowered into the resin at a height above theseparation membrane 160 based on a desired layer thickness of the firstlayer of the build 160, the controller instructs the projection system120 to irradiate selective areas of the resin between the separationmembrane 160 and the build platform 106 corresponding to a first layerof the build. The resin is configured to photocure upon exposure to theemissive spectrum of the projection system 120. More specifically, thesystem 100 can: photocure the first volume of resin to form the firstlayer of the build above the upper surface of the separation membrane160 laminated over the build window 110, the first layer of the buildadhering to a build platform 106; and retract the build platform 106 andthe first layer of the build from the separation membrane 160. Thus,upon selective irradiation, the resin photocures, thereby stronglyadhering to the build platform 106 and minimally adhering to theseparation membrane 160. Additionally, the separation membrane 160 mayadhere to the build window 110 proximal to photocured features of thefirst layer due to adhesion forces (e.g., suction forces, Stefanadhesion) between the separation membrane 160 and the build window 110.

However, the system 100 can selectively photocure a volume of resinbetween the build platform 106 and the separation membrane 160 utilizingany stereolithographic, DLP, or directed radiation technique.

5.4 Pressurization Phase

Following photocuring of the first layer of the build in Block S110, thesystem 100 can execute Block S120, which includes triggering thepressure regulation system 190 to inject a fluid (e.g., air, oxygen, aninert gas) into the interstitial region between the build window 110 andthe separation membrane 160 via the fluid distribution port 140. Whenthe interstitial region is thus pressurized, the separation membrane 160may begin to expand and to delaminate from the surface build window 110,such as from the perimeter of the build window 110 toward features ofthe current layer of the build that were cured in Block S110(hereinafter “layer features”). The separation membrane 160 may thusexert a distributed circumferential “prying” force around the perimeterof each region of layer features in the newly cured layer of the build.For example, the pressure regulation system 190 can pressurize theinterstitial region up to a pressure of 300 pascals, which may overcomeadhesion forces (e.g., suction forces, Stefan adhesion) between thebuild window 110 and the separation membrane 160.

In one implementation, the pressure regulation system 190 injects aninert fluid into the interstitial region such that any fluid permeatingthe separation membrane 160 does not inhibit photocuring of the resin.Alternatively, the system 100 includes a separation membrane 160constructed from TFE-AF or another oxygen-permeable material and thepressure regulation system 190 displaces oxygen (or oxygen-rich fluid)into the interstitial region such that an oxygenated layer forms acrossthe outer surface of the separation membrane 160 when inflated in BlockS120, thereby further preventing adhesion between the separationmembrane 160 and layer features of the current layer of the build. Inyet another alternative implementation, the system 100 can also includea separation membrane 160 that is substantially impermeable to oxygen(e.g., separation membrane 160 manufactured from crystalline PFA andcharacterized by a thickness greater than 5o microns). Thus, the system100 can inject a fluid (e.g., such as air or an inert gas) into theinterstitial region between the separation membrane 160 and the buildwindow 110, where the separation membrane 160 is characterized by lowgas permeability.

In another implementation, the system 100 does not actively inject fluidinto the interstitial region while executing Block S120 and insteadreleases the vacuum being held during execution of Block S110 allowingthe interstitial region to passively inflate.

As shown in FIG. 9, the system 100 can set a target interstitialpressure (e.g., a target absolute pressure or a target differentialpressure relative to the build chamber) in the interstitial region inBlock S120 and control the pressure regulation system 190 to reach thispressure within the interstitial region. In one implementation, thesystem 100 can set a target pressure corresponding to a targetseparation distance between the separation membrane 160 and the buildwindow 110 resulting from the target interstitial pressure. In thisimplementation, an operator of the system 100 can empirically determinethe target interstitial pressure that corresponds to a desired targetseparation distance. Alternatively, the system 100 can: evaluate aphysical model of the separation membrane 160 and interstitial region tocalculate a separation distance resulting from a range of interstitialpressures; and select a target interstitial pressure that results in thetarget separation distance.

Furthermore, because the separation distance resulting from interstitialpressure additionally depends on the weight of the resin in the resinreservoir and the ambient pressure within the build chamber, the system100 can measure these variables prior to calculating the targetinterstitial pressure. For example, the system 100 can measure depth andvolume of the resin by including a visible light camera positionedwithin the build chamber in order to record images of the resinreservoir. The system 100 can then execute computer vision techniques tocalculate a volume of resin within the resin reservoir. Alternatively,system 100 can utilize a liquid level sensor to measure the depth andcalculate the volume of the resin. Additionally, the system 100 canmeasure the temperature of the resin and access the density of the resinat the measured temperature in order to measure the total mass of theresin in the resin reservoir. The system 100 can then incorporate themass of the resin in the reservoir as a variable in the physical model(or the empirical data) for the separation distance achieved by a rangeof interstitial pressures. Thus, the system 100 can: measure a mass ofthe resin over the separation membrane 160; calculate a targetinterstitial pressure based on a mass of resin in the reservoir, thetarget interstitial pressure corresponding to a target separationdistance; and pressurize the interstitial region to the targetinterstitial pressure.

In another implementation, the system 100 can maintain the targetinterstitial pressure, during the pressurization phase, by executing afeedback control algorithm based on a current interstitial pressure.More specifically, the system 100 can: measure a series of interstitialpressures during the pressurization phase; and executeproportional-integral-derivative (hereinafter “PID”) control topressurize the interstitial region to the target interstitial pressure.

In yet another implementation, the system 100 can measure the separationdistance of the separation membrane 160 from the build window 110 andexecute a PID control algorithm to modulate the interstitial pressure,during the pressurization phase, in order to achieve a target separationdistance. More specifically, the system 100 can: measure a separationdistance of the separation membrane 160 from the build window 110 duringpressurization of the interstitial region; and adjust the targetinterstitial pressure based on the separation distance (e.g., via a PIDcontrol algorithm). In this implementation, the system 100 can include alaser distance meter configured to measure the separation distance.Additionally, the system 100 can access a separation distance profileand control this separation distance in accordance with the profile overtime via a feedback control 100p and input from the laser distancemeter.

However, the system 100 can pressurize the interstitial region to atarget interstitial pressure in any other way.

5.4.1 Selective Inflation

In one implementation, the system 100 can determine whether to excludeBlock S120 (e.g., based on the geometry of the build or the resinmaterial) from selective build cycles. The system 100 can excludeinflating the interstitial region between the build window 110 and theseparation membrane 160 when the system 100 photocures a build layerwith geometry (e.g., low cross sectional area) and material properties(e.g., high target green strength or low viscosity), such that it doesnot cause significant adhesion forces (e.g., suction forces, Stefanadhesion) between the separation membrane 160 and the build window 110.In this implementation, the system 100 does not execute Block S120 andbegins executing Block S130 after the completion of Block S110.Furthermore, in this implementation, the system 100 can also exclude therelamination phase of Block S140 (e.g., for the passive laminationvariation of the system 100).

5.4.2 Chemistry-Specific Gas Permeability

In one implementation, the system 100 includes an oxygen permeableseparation membrane 160 to allow oxygen to saturate a layer above theseparation membrane 160 within the resin for resins withoxygen-inhibited chemistries. The oxygen saturated layer can, therefore,prevent these resins from photocuring against and adhering to theseparation membrane 160 within a certain depth beyond the separationmembrane 160. In this implementation, the separation membrane 160 can beconstructed from TFE-AF. Additionally, the system 100 can include aseparation membrane 160 of a greater thickness and/or stiffness, anincreased offset between the separation membrane 160 and the buildwindow 110, and/or execute a decreased peak inflation pressure duringBlock S120 (e.g., so that the separation can diffuse oxygen into theresin without substantially deflecting). In one implementation, thepressure applied to the interstitial region between the build window 110and the separation membrane 160 is matched to the atmospheric pressureat the upper surface of the separation membrane 160 such that thepressure gradient across the separation membrane 160 is negligible.

5.5 Retraction Phase

Generally, in Block S130, the build platform 106 retracts verticallyupward away from the build window 110. More specifically, the controllerinstructs the linear actuation system coupled to the build platform 106to exert an upward force in order to separate the build from the buildwindow 110 and move the build upward. In one implementation, the system100 applies, via the linear actuation system, force over time accordingto a material specific force profile consistent with the green strengthand geometry of the build, as well as print conditions such as resintemperature and viscosity. When the sum of the upward force exerted bythe build platform 106 and the prying force of the fluid inflating theinterstitial space between the separation membrane 160 and the buildwindow 110 is sufficient to overcome the adhesion forces (e.g., suctionforces, Stefan adhesion) holding the separation membrane 160 proximal tothe layer features of the build against the build window no, theseparation membrane 160 may separate from the build window 110 and beginmoving upward with the build platform 106. However, the separationmembrane 160 may still adhere to the build as it rises upward.

The system 100 can detect the instant at which the separation membrane160 separates from the build window 110 (e.g., by measuring a change inthe force applied by the linear actuation system coupled to the buildplatform 106) and can continue to actuate the build platform 106 upwardin order to separate the separation membrane 160 from the build. As thebuild platform 106 actuates away from the build window 110, theseparation membrane 160 may continue to stretch while adhered to therising build. However, the rising build platform 106 increases the forceangle between the bottom surface of the build and the separationmembrane 160, which may cause the separation membrane 160 to peel awayfrom the build.

In one implementation, as shown in FIG. 10, the system 100 can include aload cell within the build platform 106 to measure the cumulative forcebeing applied to the build platform 106 and therefore the layer(s) ofthe build in its green state adhered to the build platform 106. Thus,the system 100 can measure the force exerted on the build platform 106and/or the adhered build during the retraction phase via a load cellintegrated with the build platform 106. Alternatively, the system 100can estimate the force applied to the build platform 106 based on thetorque of a motor configured to actuate the linear actuation system. Inthis implementation, the system 100 can execute closed-loop controlalgorithms—such as a PID control algorithm—to ensure that the peak forceapplied to the build platform 106 during the retraction phase does notexceed a maximum retraction force. The system 100 can calculate amaximum retraction force based on the green strength of the cured resinand/or the geometry of the build. For example, the system 100 can:access the geometry of the build (e.g., during the particular buildcycle); estimate the distribution of force through this geometry over arange of applied forces (e.g., at the build platform 106) to identify amaximum stress and/or strain on the build; and estimate a maximumretraction force (as measured at the build platform 106) to preventbuild failure based on the maximum stress and/or strain on the build andthe green strength and/or geometry of the build. Thus, the system 100can: access a maximum retraction force corresponding to the resin;measure a retraction force applied to the build platform 106 duringretraction of the build platform 106; and adjust an acceleration and/orvelocity of the build platform 106 based on the retraction force. Thesystem 100 can also limit overshoot in the desired force profile appliedto the build over multiple build cycles during Block S130, therebyimproving build quality and consistency.

Additionally, upon separation of the first layer of the build from thebuild window 110, the system 100 can actuate the build platform 106according to a displacement curve, which defines the displacement (andtherefore the velocity and acceleration) of the build platform 106 as ittranslates upward through the resin reservoir. The system 100 can definea displacement curve that ensures stability of the build while in itsgreen state as it moves through the (often viscous) resin within theresin reservoir and/or during the first stages of separation of theseparation membrane 160 from the build window 110. Therefore, the system100 can adjust the velocity and/or acceleration defined by thedisplacement curve based on the viscosity of the resin. For example, thesystem 100 can define a displacement curve characterized by a relativelyhigh peak velocity and a relatively high peak acceleration for a resincharacterized by a relatively low viscosity. In another example, thesystem 100 can define a displacement curve characterized by a relativelylow peak velocity and a relatively low peak acceleration for a resincharacterized by a relatively high viscosity. Thus, the system 100 can:define a displacement curve for the build platform 106 based on a targetgreen strength of the resin and a viscosity of the resin; and retractthe build platform 106 according to the displacement curve.

5.6 Relamination Phase

Generally, in Block S140, the pressure regulation system 190 evacuatesfluid from (e.g., depressurizes) the interstitial region, therebypulling the separation membrane 160 taught across the surface of thebuild window 110. Additionally, by pulling the separation membrane 160downward toward the build window 110, the system 100 can increase therate of separation between the separation membrane 160 and the buildand/or reduce the total retraction distance needed to peel theseparation membrane 160 away from the build. Furthermore, bydepressurizing the interstitial region between the separation region andthe build window no, the system 100 ensures that the separation membrane160 is laminated against the build window 110 such that there are 110bubbles or wrinkles in the separation membrane 160 before the system 100photocures a second layer in Block S150. More specifically, the system100 can, via the pressure regulation system 190, reduce the differentialpressure within the interstitial region relative to the build chamber inorder to generate a downward force on the separation membrane 160 thatcauses the separation membrane 160 to separate from the newly curedlayer of the build, if the separation membrane 160 has not alreadyseparated from the newly cured layer of the build due to retraction ofthe build platform 106 in Block S120. Furthermore, by reducing thedifferential pressure across the separation membrane 160, the system 100can also increase the angle of separation of the separation membrane 160from the build, thereby increasing the rate at which the separationmembrane 160 may peel away from the newly cured layer of the build.

In one implementation, the system 100 can further decrease thedifferential pressure between the build chamber and the interstitialregion by concurrently increasing the absolute pressure in the buildchamber while decreasing the absolute pressure in the interstitialregion. Thus, the system 100 can: pressurize a build chamber above theseparation membrane 160 while evacuating the fluid from the interstitialregion in order to further increase the force across the separationmembrane 160 and improve separation of the separation membrane 160 fromthe newly cured layer of the build. By increasing the absolute pressurewithin the build chamber, the system 100 can also hasten the flow ofresin underneath the retracted build platform 106 and adhered build inaddition to increasing the force across the separation membrane 160.

5.7 Advancement Phase

In one implementation, as shown in FIG. 11, the system 100 executes anadvancement phase by actuating the build platform 106 and adhered buildvia the linear actuation system to a distance relative to the separationmembrane 160 such that the bottom surface of the build is a distanceabove the upper surface of the separation membrane 160 approximatelyequal to the desired layer thickness of the subsequent layer of thebuild in Block S142, or at or above a distance above the separationmembrane 160 in preparation for the subsequent photocuring phase ofBlock S150. The system 100 can execute an advancement phase inimplementations where the system loo retracts the build platform 106farther than the layer thickness of the build in order to improve theangle of separation of the separation membrane 160 against the bottomsurface of the build. Thus, by increasing the retraction distance, thesystem 100 can increase this separation angle and therefore moreeffectively peel the separation membrane 160 away from the newly curedlayer of the build. However, before photocuring a subsequent layer, thesystem 100 can advance the build (downward and toward the build window110) such that the newly cured layer is offset from the surface of theseparation membrane 160 (that is laminated to the build window 110) bythe preset layer thickness for the build—enabling the system 100 tophotocure a subsequent layer between the current layer and the uppersurface of the separation membrane 160. More specifically, the system100 can: advance the build platform 106 toward the build window 110 to atarget position above the separation membrane 160 laminated to the buildwindow 110, the target position based on a layer thickness parameter ofthe build; and photocure the second volume of resin to form the secondlayer of the build between the upper surface of the separation membrane160 and the first layer of the build. In one implementation, furtherdescribed below the system 100 can advance the build platform 106 to thesame vertical position of the previous layer in order to cure adifferent selective volume of the same layer in the subsequentphotocuring phase of Block S150. Additionally or alternatively, thesystem 100 can advance the build platform 160 to a vertical positionenabling the system 100 to photocure a layer that overlaps with theprevious layer in order to generate interlocking structures.

Additionally or alternatively, also shown in FIG. 11, the system 100 canexecute an advancement delay between the relamination of the separationmembrane 160 in the relamination phase and the advancement phase inorder to allow the resin to settle in preparation for photocuring asubsequent layer. Furthermore, the system 100 can access (from anempirical data table) or calculate an advancement delay sufficient toallow the resin to flow back into position underneath the build andbuild platform 106. Thus, the system 100 can prevent translational flowin the resin reservoir caused by movement of the build platform 106 andthe adhered build from affecting the features of the build duringadvancement of the build platform 106 in the resin reservoir prior tophotocuring a subsequent layer of the build. More specifically, thesystem 100 can: access an advancement delay corresponding to theviscosity of the resin; and, during the advancement phase delayed fromthe relamination phase by the advancement delay, advance the buildplatform 106 toward the build window 110 to the target position abovethe separation membrane 160 laminated to the build window 110, thetarget position based on the layer thickness parameter of the build.

In another implementation, the system 100 can set an advancement speedand/or acceleration for the build platform 106 as it advances into orwithin the resin during the advancement phase. The system 100 can access(from an empirical data table) or calculate an advancement speed basedon the distance of the build from the build window 110, the viscosity ofthe resin, the green strength of the resin, and/or the geometry of thebuild. For example, the system 100 can estimate the forces that may beimparted by the resin on the build upon insertion of the build into theresin reservoir over a range of advancement speeds. The system 100 canthen select an advancement speed that the system 100 predicts willresult in forces imparted to the build that are less than a thresholdforce. More specifically, the system 100 can: access a targetadvancement speed based on a viscosity of the resin and a geometry ofthe first layer of the build; and advance the build platform 106 towardthe target position at the target advancement speed. Alternatively, thesystem 100 can: access an advancement profile specifying verticalpositions of the build platform 106 over time; and actuate the linearactuation system according to this advancement profile during executionof Block S140 (e.g., according to feedback control algorithms), therebyenabling modulation of the advancement speed and/or acceleration overtime.

7.1 Timing Variations

Generally, the system 100 executes Blocks S120, S130, and S140, insequence as described above. However, as shown in FIGS. 12A, 12B, and12C, the system 100 can execute Block S120 and S130 and/or Blocks S130and S140 in an overlapping manner, thereby increasing build speeds.Additionally or alternatively, the system 100 can execute pauses betweenany Block of the method S100 to improve print conditions during anyBlock. In one implementation, shown in FIG. 12A, the pressurizationphase and the retraction phase can overlap, enabling faster separationbetween the build and the build window 110. For example, thepressurization phase can begin and, as the system 100 approaches thetarget interstitial pressure, the system 100 can begin to retract thebuild platform 106 in the retraction phase. More specifically, thesystem 100 can, during the retraction phase concurrent with thepressurization phase, retract the build platform 106 from the buildwindow 110.

In another implementation, shown in FIG. 12B, the system 100 can beginthe relamination phase while the system 100 is still retracting thebuild platform 106 such that the separation membrane 160 can peel awayfrom the build at a higher rate and relaminate to the build window 110more quickly. In one example, the system 100 can forgo an advancementdelay by initiating the relamination phase while the build platform 106is still retracting providing time for the resin to flow underneath thebuild platform 106 as the build platform 106 moves upward. Morespecifically, the system 100 can, during the relamination phaseconcurrent with the retraction phase, evacuate the fluid from theinterstitial region to peel the separation membrane 160 from the firstlayer of the build and laminate the separation membrane 160 to the buildwindow 110.

In yet another implementation, shown in FIG. 12C, the system 100 canoverlap the pressurization phase and the retraction phase and theretraction phase and the relamination phase, thereby further reducingthe duration of the build cycle. Additionally or alternatively, thesystem 100 can modulate the interstitial pressure and the retractionspeed in coordination with the overlapping phases. For example, thesystem 100 can detect separation of the newly cured layer from the buildwindow 110 (e.g., based on force and/or acceleration detected at thebuild platform 106) and, in response to separation of the newly curedlayer from the build window no, begin evacuating fluid from theinterstitial region. In another example, the system 100 can increase aretraction speed of the build platform 106 while concurrently initiatingthe relamination phase in order to more effectively peel the separationmembrane 160 from the newly cured layer of the build.

5.7.2 Successive Photocuring Phases

Upon execution of Blocks S120, S130, S140, and/or S142, the system 100executes Block S150 to photocure a second layer of the build. Once thebuild platform 106 and adhered build are at a target offset from thesurface of the separation membrane 160, the system 100 can selectivelyphotocure a second volume of the resin between a surface of the layerfeatures of the previously photocured layer and the upper surface of theseparation membrane 160 corresponding to a second cross-section of thebuild in order to connect this second cross-section to the previouslayer of the build (i.e. a second layer of the build). Upon photocuringthe second layer of the build, the second layer may strongly adhere tothe first layer of the build while minimally adhering to the separationmembrane 160.

Once the system 100 photocures a second layer of the build, the system100 can again execute Blocks S120, S130, and S140 to separate the bottomsurface of the second layer from the upper surface of the separationmembrane 160 and the build window 110. However, in implementationsdescribed below, the system 100 can execute variations of Blocks S120,S130, and S140 while separating the second layer of the build whencompared to the separation of the first layer based on changes in thegeometry of the build (e.g., via the addition of subsequent layers). Forexample, the system 100 can modify (e.g., reduce or increase) themaximum retraction force, during the retraction phase, based on theaddition of new features in a subsequent layer. In another example, thesystem 100 can modify (e.g., reduce or increase) the target interstitialpressure based on features in a current layer of the build. In yetanother example, the system 100 can modify the displacement curve duringthe retraction phase based on the addition of new features in subsequentlayers. In an additional example, the system 100 can modify theadvancement speed based on the geometry of subsequent layers.

5.7.3 Print Parameters

In one implementation, the system 100 can adjust or set print parametersfor a build based on the resin selected for the build and/or thegeometry of the build. For example, if the system 100 receives a resinselection for the build that is characterized by a relatively low greenstrength and/or a geometry of the build characterized by relatively finefeatures, the system 100 can broadly reduce the speed of the buildand/or the maximum forces allowable at each phase of the build in orderto prevent build failure and/or poor dimensional accuracy. In analternative example, if the system 100 receives a resin selection forthe build that is characterized by a relatively high green strengthand/or a geometry of the build characterized by relatively robustfeatures, the system 100 can broadly increase the speed of the build andthe maximum forces allowable at each phase of the build to increase thespeed of the build cycle and therefore decrease manufacturing time.

In one implementation, the system 100 can increase the overlap betweenphases of the build cycle in response to receiving a more robust buildgeometry or a resin selection characterized by a high green strength.Thus, the system 100 can: receive a selection of the resin for thebuild; receive a geometry of the build; and calculate a set of buildparameters corresponding to the selection of the resin and the geometryof the build, the build parameters specifying a duration of thepressurization phase, a duration of the retraction phase, a duration ofthe relamination phase, an overlap between the pressurization phase andthe retraction phase, and an overlap between the retraction phase andthe relamination phase.

However, the system 100 can modify any aspect of the build processdescribed above in response to particular features present in thegeometry of the build and/or the properties (e.g., viscosity and/orgreen strength) of the resin selected for the build.

5.7.4 Double Separation

In one implementation, the system 100 photocures a single layer in twoor more separation stages. Generally, the system 100 can adapt theexecution of the method S100 to the particular geometry of the build,even within the same layer. The system 100 can execute two or morestages of the same layer and execute different variations of BlocksS120, S130, and S140 for each stage.

More specifically, the system 100 photocures the first stage of a layerincluding a first set of layer features and separates the first stage ofthe layer by executing Blocks S110, S120, S130, and S140. Then, in asecond stage, the system 100 instructs the linear actuation system toreturn the build platform 106 to its initial position in Block S110before selectively photocuring a second volume of the resincorresponding to a second set of layer features within the same layer.After the system 100 photocures a second set of layer features for thefirst layer, the system 100 can execute different variations of BlocksS120, S130, and S140 to separate the second stage of the layer. Forexample, the system 100 can photocure the first set of layer features ofthe layer and separate the first set of layer features from theseparation membrane 160 by executing Blocks S120, S130, and S140; then,to separate the second set of layer features, the system 100 can executeBlocks S130 and S140 (i.e. by instructing the linear actuation system tomove the build platform 106 upward without first inflating theinterstitial region between the separation membrane 160 and the buildwindow 110). In this example, the system 100 can photocure a first setof layer features and separate using the inflation process of Block S120and then successively photocure a second more delicate set of layerfeatures by omitting the inflation step of Block S120. However, any ofthe aforementioned implementations of the method S100 can be executed insuccession in different stages of the same layer.

5.7.5 Inter-Layer Feedback

In one implementation, the system 100 can analyze force data recorded atthe linear actuation system during the execution of Block S130 for afirst layer to calculate changes in the maximum retraction force duringthe retraction phase, the retraction force/displacement profile, thetarget interstitial pressure for the pressurization phase, and/or thestrength of the vacuum applied during the relamination phase in BlocksS130, S120, and S140 respectively. Additionally, the system 100 cancalculate changes to the advancement profile during the advancementphase. Thus, the system 100 analyzes data collected during the executionof a first layer to improve the separation process for a second layer.In one implementation, the system loo can increase the duration and/orthe target interstitial pressure during Block S120 in response to a highpeak force recorded during Block S130 during the separation of aprevious layer. Additionally or alternatively, the system 100 can reducethe duration and/or the target interstitial pressure during Block S120in response to a low peak force recorded during Block S130 of aseparation of a previous layer.

However, the system 100 can adjust the maximum retraction force appliedby the linear actuation system in Block S130, the target interstitialpressure in Block S120, and/or the strength or duration of the vacuumapplied in Block S140 in response to force data recorded duringseparation of a previous layer of the build.

5.7.6 Failure Detection

In one implementation, the system 100 can analyze force data and/or anyother data collected during the separation of a previous layer of thebuild to detect a failure in the separation process. For example, thesystem 100 can analyze force data recorded during the separation of aprevious layer to detect a sudden reduction in applied force at thelinear actuation system incongruent with the change in layer geometrycorresponding to a failure of the build. Additionally or alternatively,the system 100 can include a camera and can execute optical detectionmethods utilizing computer vision techniques to corroborate forceprofile data indicating a build failure. In one implementation, thesystem 100 can detect a failure in the separation membrane 160 and/orbuild window 110.

Upon detecting a build failure, the system 100 can notify a user thatthe build has failed and can recommend changes to the build settings toavoid a failure in a subsequent build attempt.

The systems and methods described herein can be embodied and/orimplemented at least in part as a machine configured to receive acomputer-readable medium storing computer-readable instructions. Theinstructions can be executed by computer-executable componentsintegrated with the application, applet, host, server, network, website,communication service, communication interface,hardware/firmware/software elements of a user computer or mobile device,wristband, smartphone, or any suitable combination thereof. Othersystems and methods of the embodiment can be embodied and/or implementedat least in part as a machine configured to receive a computer-readablemedium storing computer-readable instructions. The instructions can beexecuted by computer-executable components integrated bycomputer-executable components integrated with apparatuses and networksof the type described above. The computer-readable medium can be storedon any suitable computer readable media such as RAMs, ROMs, flashmemory, EEPROMs, optical devices (CD or DVD), hard drives, floppydrives, or any suitable device. The computer-executable component can bea processor but any suitable dedicated hardware device can(alternatively or additionally) execute the instructions.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the embodiments of the invention without departing fromthe scope of this invention as defined in the following claims.

I claim:
 1. A method for additive manufacturing comprising: during afirst photocuring phase: laminating a separation membrane over a buildwindow by depressurizing an interstitial region between the separationmembrane and the build window; and photocuring a first volume of a resinto form a first layer of a build at a surface of the separationmembrane; injecting a fluid between the separation membrane and thebuild window to inflate the separation membrane; retracting the firstlayer of the build from the build window to peel the separation membranefrom the first layer of the build; and during a second photocuringphase: laminating the separation membrane over the build window bydepressurizing the interstitial region between the separation membraneand the build window; and photocuring a second volume of the resin toform a second layer of the build between the surface of the separationmembrane and the first layer of the build.
 2. The method of claim 1:wherein laminating the separation membrane over the build window duringthe first photocuring phase comprises laminating the separation membraneover the build window by depressurizing the interstitial region whilephotocuring the first volume of the resin to form the first layer of abuild during the first photocuring phase; and wherein laminating theseparation membrane over the build window during the second photocuringphase comprises laminating the separation membrane over the build windowby depressurizing the interstitial region while photocuring the secondvolume of the resin to form the second layer of the build during thesecond photocuring phase.
 3. The method of claim 1: wherein laminatingthe separation membrane over the build window by depressurizing theinterstitial region during the first photocuring phase comprisesgenerating a first negative pressure gradient across the separationmembrane by depressurizing the interstitial region during the firstphotocuring phase; and wherein laminating the separation membrane overthe build window by depressurizing the interstitial region during thesecond photocuring phase comprises generating a second negative pressuregradient across the separation membrane by depressurizing theinterstitial region during the second photocuring phase.
 4. The methodof claim 3: wherein generating the first negative pressure gradientacross the separation membrane by depressurizing the interstitial regionduring the first photocuring phase comprises generating the firstnegative pressure gradient across the separation membrane bydepressurizing the interstitial region during the first photocuringphase, the first negative pressure gradient greater than 200 pascals;and wherein generating the second negative pressure gradient across theseparation membrane by depressurizing the interstitial region during thesecond photocuring phase comprises generating the second negativepressure gradient across the separation membrane by depressurizing theinterstitial region during the second photocuring phase, the secondnegative pressure gradient greater than 200 pascals.
 5. The method ofclaim 1, further comprising pressurizing a build chamber containing agaseous environment above the separation membrane.
 6. The method ofclaim 5: wherein laminating the separation membrane over the buildwindow by depressurizing the interstitial region during the firstphotocuring phase comprises generating a first negative pressuregradient across the separation membrane by depressurizing theinterstitial region relative to the pressurized build chamber during thefirst photocuring phase; and wherein laminating the separation membraneover the build window by depressurizing the interstitial region duringthe second photocuring phase comprises generating a second negativepressure gradient across the separation membrane by depressurizing theinterstitial region relative to the pressurized build chamber during thesecond photocuring phase.
 7. A method for additive manufacturingcomprising: at a first time prior to a first photocuring phase, drawinga first vacuum between a separation membrane and a build window tolaminate the separation membrane to the build window; during a firstphotocuring phase, photocuring a first volume of a resin to form a firstlayer of a build at a surface of the separation membrane; inflating aninterstitial region between the separation membrane and the build windowto delaminate the separation membrane from the build window; retractingthe first layer of the build from the build window to peel theseparation membrane from the first layer of the build; at a second timeprior to a second photocuring phase, drawing a second vacuum between theseparation membrane and the build window to laminate the separationmembrane to the build window; and during a second photocuring phase,photocuring a second volume of the resin to form a second layer of thebuild between the surface of the separation membrane and the first layerof the build.
 8. The method of claim 7, wherein inflating theinterstitial region to delaminate the separation membrane from the buildwindow comprises releasing the first vacuum to delaminate the separationmembrane from the build window.
 9. The method of claim 8, whereinreleasing the first vacuum to delaminate the separation membrane fromthe build window comprises: opening an external air port; and passivelyinflating the interstitial region to an ambient air pressure.
 10. Themethod of claim 7, wherein retracting the first layer of the build fromthe build window comprises retracting the first layer of the build fromthe build window while inflating the interstitial region.
 11. A methodfor additive manufacturing comprising: at a first time prior to a firstphotocuring phase, laminating a separation membrane to a build window;during a first photocuring phase, photocuring a first volume of a resinto form a first layer of a build at a surface of the separationmembrane; injecting a fluid between the separation membrane and thebuild window to inflate the separation membrane; retracting the firstlayer of the build from the build window; at a second time prior to asecond photocuring phase, laminating the separation membrane to thebuild window; and during a second photocuring phase, photocuring asecond volume of the resin to form a second layer of the build betweenthe surface of the separation membrane and the first layer of the build.12. The method of claim 11: wherein laminating the separation membraneto the build window at the first time comprises depressurizing aninterstitial region between the separation membrane and the build windowat the first time; wherein injecting the fluid between the separationmembrane and the build window comprises pressurizing the interstitialregion; and wherein laminating the separation membrane to the buildwindow at the second time comprises depressurizing the interstitialregion at the second time.
 13. The method of claim 11: whereinlaminating the separation membrane to the build window at the first timecomprises laminating the separation membrane to the build window at thefirst time and maintaining lamination of the separation membrane to thebuild window during the first photocuring phase; and wherein laminatingthe separation membrane to the build window at the second time compriseslaminating the separation membrane to the build window at the secondtime and maintaining lamination of the separation membrane to the buildwindow during the second photocuring phase.
 14. The method of claim 11,wherein laminating the separation membrane to the build window at thefirst time comprises laminating the separation membrane to the buildwindow at the first time, the separation membrane offset from the buildwindow by greater than 50 microns prior to the first time.
 15. Themethod of claim 11, wherein retracting the first layer of the build fromthe build window comprises retracting the first layer of the build fromthe build window to peel the separation membrane from the first layer ofthe build.
 16. The method of claim 15, wherein laminating the separationmembrane to the build window at the second time comprises laminating theseparation membrane to the build window at the second time to peel theseparation membrane from the first layer of the build.
 17. The method ofclaim 11, wherein laminating the separation membrane to the build windowat the second time comprises laminating the separation membrane to thebuild window at the second time while retracting the first layer of thebuild from the build window.
 18. The method of claim 11, whereinretracting the first layer of the build from the build window comprisesretracting the first layer of the build from the build window whileinjecting the fluid between the separation membrane and the buildwindow.
 19. The method of claim 11: wherein retracting the first layerof the build from the build window comprises retracting the first layerof the build from the build window while injecting the fluid between theseparation membrane and the build window, wherein laminating theseparation membrane to the build window at the second time compriseslaminating the separation membrane to the build window at the secondtime while retracting the first layer of the build from the buildwindow.
 20. The method of claim 19, wherein laminating the separationmembrane to the build window at the second time while retracting thefirst layer of the build from the build window comprises, afterinjecting the fluid between the separation membrane and the buildwindow, laminating the separation membrane to the build window at thesecond time while retracting the first layer of the build from the buildwindow.